This invention relates to buckle-type sheet folding machines and more particularly to an automatic mechanism for adjusting the position of the paper stops in the fold pan of such buckle-type sheet folding machines.
Buckle-type sheet folding machines typically comprise a series of rollers and fold-pan assemblies. A sheet of paper to be folded is inserted between two rotating rollers of a first roller set and is driven by these two rollers into a first fold-pan of a first fold-pan assembly. A forward edge of the sheet eventually strikes a paper stop in the fold pan. However, the two rollers continue to feed the sheet forward. This feeding continues until the sheet buckles, and the bulge of the buckle eventually extends between two rollers of a second roller set. These rollers fold the sheet at the bulge and feed this folded edge into a second fold-pan of a second fold-pan assembly.
Upon striking a second paper stop, there is a new buckle formed in the sheet and this buckle is, in turn, inserted between two rollers of a third roller set. This process continues until the sheet is folded a desired number of times. A typical folding machine may fold a sheet several times. In most buckle-type folding machines, the paper stops in the fold-pan assemblies are adjustable so that the positions of the folds on the paper sheets can be controlled. An example of such a fold-pan assembly is taught in Boyer, U.S. Pat. No. 3,856,293.
However, problems exist in prior art sheet folding apparatuses. In many such apparatuses, it is difficult to adjust accurately the positions of the paper stops. Some adjustments on the fold-pan assemblies are difficult to get to because of the position of the fold-pan assembly within the folding machine. Moreover, skilled operators are required because of the complexity of setting up the pan-fold assemblies from job to job.
Another problem which exists in the art is the need to make folds on sheets which are perpendicular or parallel with the printed matter on such sheets. Normally, paper stops on the fold-pan assemblies are perpendicular with the longitudinal axes of the fold-pans so that the sheet edges registered by paper stops are also perpendicular with longitudinal axes of the fold-pans. the resulting folds of such sheets are parallel with these registered edges. However, it is often the case that printed material on the sheets is not perpendicular or parallel with the sheets edges. Some printing on the sheets may be skewed slightly. Therefore, it is sometimes desirable to cause these sheets to register at slight angles relative to the fold-pan's longitudinal axes so that the folds may be made square with the printed material. In prior art devices, such skewing is difficult to accomplish.
Finally, yet another problem with prior art fold-pan assemblies is that they have no provision to handling sheet material having tabs extending therefrom. Such tabbed sheet material could previously be folded only by the use of special folding machines and, typically, could not be folded in prior art fold-pan assemblies.
Accordingly, the need still exists in the art to provide a fold-pan assembly which can be adjusted readily and rapidly by relatively inexperienced operators and which can be adjusted both for skewed printing and for tabbed sheet material.